In recent years, as a source that causes global warming, a greenhouse effect that is caused by CO2 was pointed out, and a countermeasure thereof has been an international urgent task for keeping the global environment. Sources of the generation of CO2 reach all the fields of human activities that incinerate fossil fuels, and the request for suppressing the discharge of CO2 tends to be stronger. In accordance with this, a method of eliminating and recovering CO2 contained in exhaust gas by bringing the exhaust gas of a boiler into contact with an amine-based CO2 absorbent such as an alkanolamine aqueous solution and a method of storing recovered CO2 without discharging it into the air for power generating facilities such as thermal power plants using a large amount of fossil fuels have been aggressively researched.
Conventionally, in Patent Literature 1, a method of eliminating CO2 (carbon dioxide) and SOx (sulfur oxide) that are included in the exhaust gas is disclosed. This method includes: a denitration process in which NOx (nitrogen oxide) contained in the exhaust gas is reduced so as to be denitrated; a desulfurization process in which SOx contained in the exhaust gas is desulfurized by being brought into contact with calcium carbonate included in sludge; a de-CO2 process in which CO2 included in the exhaust gas is absorbed into an absorbent by bringing the exhaust gas for which the denitration process and the desulfurization process have been performed into concurrent contact with an amine-based absorbent (alkanolamine aqueous solution) at an absorber; and an absorbent regenerating process in which a lean solution acquired by eliminating CO2 from a rich solution that has absorbed CO2 at a regenerator is returned to the absorber. In this method, in order to prevent a situation in which a heat-stable salt generated by oxidizing alkanolamine with oxygen included in the exhaust so as to be degraded or reacting alkanolamine with remaining NOx or remaining SOx and a degraded material including a solid matter such as a dust included in the exhaust gas are accumulated within a system through which the absorbent passes, reclaiming is performed in which the absorbent is heated in a reclaimer, the degraded material is concentrated as sludge, and the degraded material is eliminated from the absorbent.